TIRES

Tires should be checked at least once a month, or at every fill-up. Check tire pressure and the condition of all four tires.
 

Checking Tire Pressure
 

1. Ideally, check tire pressure when the tires are cold

2. Remove the valve stem cap

3. Push the pressure gauge firmly on the valve stem until the hissing sound stops

4. Read the measurement on the pressure gauge

5. Add air if necessary, then recheck the pressure

6. Put the valve stem cap back on

7. Repeat on the other tires, including the spare

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​How to Read a Tire Pressure Gauge
There are three types of tire pressure gauges – pencil, digital, and dial. Digital gauges will need batteries in order to work.

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A close-up of a car tire.

• A pencil style is read by looking at the highest number visible on the extending slider, each line equaling 1 psi.

• A digital gauge will display the pressure on the screen.

• A dial gauge has a needle that will point to the pressure.

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What does it mean to check the tire pressure when cold?
It's best to check tire pressure when the tires are “cold” - meaning they haven't been driven for more than a few miles. If you check the tire pressure when the tires are “hot”, they will read about 4 psi higher than they would if cold. This is normal.

If you need to adjust the tire pressure when the tires are hot, add air until they are about 4 psi higher than the recommended cold tire pressure. Be sure to recheck the pressure next time the tires are cold again. 
 

• If tire pressure is too low, too much of the tire touches the road. This results in reduced fuel economy, and also the possibility of tire overheating. Also, the tires will wear excessively at the edges of the tread area.

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• If tire pressure is too high, the vehicle will have reduced traction and braking ability as too little of the tire contacts the road. The tires can be more easily damaged by road debris and potholes, and the ride quality will be harsher. Over time, the tires will wear excessively in the center of the tread area.

How do I know how much air to put in my tires?
The optimal tire pressure for a vehicle can be found in the owner's manual or on the tire placard, a sticker that is usually located in the driver's door jamb. Note that front and rear tires may require different pressures.
 

• Do NOT use the “max. pressure” printed on the sidewall of the tire. This is the absolute maximum pressure the tire can hold and is often much higher than the tire pressure specified by the manufacturer for optimum performance.

• If for whatever reason you cannot find the specified tire pressure for your vehicle, 30-35 psi is a safe estimate for passenger cars.

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• Tires loose about 1-2 psi per month on average.

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• Tire pressure varies with temperature. It decreases by about 1 psi for every 10 degree drop in temperature, and increases by about 1 psi for every 10 degree increase in temperature.

Checking Tread Depth
If one or more tires become too worn, they will need to be replaced. Checking tread depth is the most common way to evaluate tire wear, and is easy to do. It's often measured with a tread depth gauge in 32nds of an inch or in millimeters.
 

1. Place the gauge in the deepest part of the tread

2. Read the gauge

3. Repeat on the remaining three tires

If you don't have a tread depth gauge, you can use the well-known “penny” test instead. Place a penny into the tread upside down, with Lincoln's head facing you. If you can see the top of Lincoln's head, your tire has less than 2/32” of tread remaining and it's time to replace it. For comparison, brand new tires have about 10/32” of tread on average.
 

What is the minimum tread depth I should have?
Most states require a minimum legal tread depth of 2/32”. However, Consumer Reports along with many service centers are starting to recommend replacement at 4/32” instead, due to poor traction in rain and snow at 2/32”.
 

• If you use a penny because you don't have a tread depth gauge, simply repeat the penny test with a quarter. If you can see the top of Washington's head, then your tires have less than 4/32”.

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• Note that it's not uncommon for tires to wear unevenly. To check for this, check the tread depth in the center, inside, and outside area of the tread.

• Tires with too little tread (often referred to as “bald”) will have poor traction on wet and snowy roads, increased braking distance, and are more likely to hydroplane. They are also more prone to blowouts and damage from road debris.

• Bald tires on the front of car can lead to understeering, which means the car doesn't turn as much as expected when the steering wheel is turned. This is because the front tires loose traction when corning, which results in the vehicle sliding forward even though the wheels are turned.

• Bald tires on the back of a car can lead to oversteering, which means the car turns more sharply than expected when the steering wheel is turned. This is because the rear tires loose traction when corning, which results in the back end swinging out (fishtailing).

Tread Wear Indicators
Tires are often designed with built-in wear indicators or wear bars, shallow rubber bars that run perpendicular to the tread pattern. They can be difficult to see compared to the much deeper grooves of the tread, but become more visible as the tire wears out. At 2/32” these bars become flush with the tread pattern, indicating the tire needs to be replaced. 
 

Tire Condition
Although important, tread wear is not the only thing to consider when looking at a tire's condition. Also check for:
 

• Nails, screws, or other embedded objects

• Damage to the sidewall or tread (cuts, scrapes, etc.)

• Bulges in the sidewall or tread

• Uneven tread wear

• Tread separation

• Metal wires visible sticking out from anywhere on the tire

• Cracks in the tire, known as weather checking or weather cracking

​​Tire Repair or Replacement
Punctures in the tread area of a tire can usually be repaired, but if the sidewall is punctured then the tire must be replaced. Any other tire damage is unrepairable. 
 

• Never drive on a flat or damaged tire.

• Uneven tread wear is an indicator of other issues. Have the vehicle checked for loose parts or poor alignment.

• If only two tires are replaced rather than all four, the new ones should always be put on the back of the vehicle. This provides the best traction and is recommended by almost all tire manufacturers due to safety concerns.

• Have your tires rotated every other oil change to help them wear more evenly.

Avoid using canned tire inflators (e.g. “Fix-a-Flat” and similar products) if at all possible. It's not a permanent fix, may damage TPMS systems, and can make later repairs difficult for your service center.
 

Get Your Vehicle Serviced if You Notice:
 

• Excessive wear, cracks, or any damage on your tires

• Nails, screws, or other items embedded in the tire

• One or more tires have a leak (go flat overnight, etc.)

• Changes in vehicle handling or steering